Hinges with at least two leaves pivotably connecting structural members are known. In these hinges, the leaves generally have knuckles defining concentrically aligned cylindrical bores therethrough. A pin is inserted within the bores of the knuckles of both leaves, pivotably connecting the leaves. The bodies of the leaves are connected to the structural members.
One type of pinned hinge is known as a "butt" or "mortise" hinge. Two or more of these hinges are commonly used to hang a door from a door frame. In butt hinges, the length of each pin is short compared to the length of the door or other structural member mounted to the hinge.
"Piano" hinges are similar to mortise hinges, except that the length of the hinge and its pin usually runs most of the length of one of the attached structural member. These hinges are sometimes known as "continuous hinges".
To seal the gaps between a door and a frame between individual mortise hinges, the leaves of the hinges are often recessed or inletted into the door and the frame to a depth equal to the thicknesses of the leaves. This permits the leaves to lie flush with both the door and the frame to produce a closer fit and allow sealing when the door is closed. This is usually not necessary with piano hinges because the leaves extend approximately the whole length of the door, spanning gaps that would otherwise exist between individual mortise hinges.
To decrease gaps between opposing leaves themselves, the leaves can be swaged. Swaging involves deforming flat leaf bodies, ideally so that the leaf bodies remain parallel and can contact or almost contact each other when the door is closed.
Bearings have been placed between leaf knuckles to reduce friction between adjacent knuckles. U.S. Pat. No. 4,097,959, for example, shows ball bearings placed between knuckles of opposed leaves and the pin. U.S. Pat. No. 3,499,183, for instance, discloses the use of bushings to lower hinge friction. Washer type bushings or bearings have also been placed between adjacent knuckles.
Hinge leaves have also been pivotally biased with respect to one another to produce a self opening or closing door. U.S. Pat. No. 4,583,262 shows a hinge in which a spring coils around a split pin and resiliently biases one leaf of the hinge with respect to the other.
The knuckles of known pinned hinges, however, are exposed. This allows debris to collect within the moving parts and bearing surfaces within the hinge, causing wear, squeaking, binding, and premature hinge failure. Lubricants on the knuckles so exposed can wash away or dry out. Also, exposed knuckles are susceptible to weather that can speed corrosion of the moving parts.
Exposed pinned hinges are also subject to vandalism. The knuckles in doors that open outwardly of a building, as required by many fire codes, are located on the outside of a door. The pins retaining these knuckles are subject to removal from the outside, effectively enabling disassembly of the door and permitting unauthorized entry.
Various methods exist for retaining the pin within the knuckles. These methods include inserting a cross-pin through the pin and the knuckles; providing a knurled surface on the pin to create an interference fit with the knuckle bores; and providing one end of the pin with a wide stop that is too big to fit through the bores, and flaring out the other end of the pin once it is inserted in the knuckles. Even with these precautions, the knuckles and the pin still remain exposed and accessible to vandals.
Finally, exposed hinges generally have distracting and unsightly knuckles that extend outwardly from the plane of the door. Once corrosion sets in, exposed surfaces of these hinges become even less attractive.
U.S. Pat. No. 4,999,879 discloses a continuous hinge that is not pinned, but has a clamp that covers two hinge members. The hinge members lack knuckles and thus lack a pin to join them pivotably. Instead, the hinge members are retained laterally by the clamp against a rod fitted therebetween. The clamp and the hinge members have geared surfaces in mesh with each other. The rod keeps the hinge members in contact with the clamp, but cannot alone keep the hinge members from separating radially. This hinge relies on the clamp to pivotably join and retain the hinge members together. Thus, the clamp must be constructed with sufficient strength to support all lateral loads imposed on the hinge members. The clamp cannot be tailored to have merely sufficient strength for another intended purpose, other than joining the hinge members laterally and pivotably, such as protecting the internal hinge components from vandalism or from the elements, or for simply improving hinge aesthetics by covering moving parts. The clamp must be significantly overbuilt if this hinge is chosen merely for a function such as these. Also, as the disclosed hinge lacks interposed knuckles from the hinge members, the hinge requires the addition of thrust bearings to prevent relative, longitudinal movement between the hinge members that must be able to resist shearing between the members. Such a thrust bearing is not essential in pinned hinges because the interposed knuckles prevent relative longitudinal movement therebetween.
A need exists for a pinned hinge whose knuckles are protected and concealed by a cover. This need is especially present for a covered pinned hinge that permits pivotal movement over more than 100.degree., and especially more than 120.degree. or 180.degree..